Heater unit for cathodes of vacuum tubes and method of producing same



May 10, 1932.

W. J. SKHNNER HEATER UNIT FOR CATHODES OF VACUUM TUBES AND METHOD OF.PRODUGING SAME Filed Feb: 7, 1931 2 Sheets-Sheet 1 INVENTOR. Walim' I J'kmnfir MW M ' ATTORNEYS.

y 1933?- w. J. SKENNER ,858,063

HEATER UNIT FOR CATHODES OF VACUUM TUBES AND METHOD OF PRODUCING SAME Filed Feb. 7, 1931 2 Sheets-Sheet 2 INVENTOR.

Waherl J75 z'rz ner M a w M ATTORNEYS.

Patented May 10, 1 932 -UNITED STATES PATENT?" OFFICE J. 51mm 01' BIIOOKIIELD, NEW JERSEY, ASSIGNOR TO VAN WICKLAND IBODUC'IB 00., O! NEWARK, NEW mSEY, A CORPORATION OF NEW JERSEY Application filed February 7, 1881.

This invention relates to heater units for the cathodes of vacuum tubes, and to a method of producin' the same. a

More particu arly the invention provides an im rovement in heater units for cathode tubes 1n which the filament is given the form of a return helix, and aims to rovide improved means for supportin an insulating such filaments. The particu ar means adopted for carrying out the object in the pre ferred form consists of insulating collars throu h which the wires of the filament are three ed.

The invention also includes a method of producing the improved heater unit.

While preferred forms of the invention are disclosed herein for purposes of illus tration, it should be understood that various changes may be made in the structure or method without departing from the spirit and scope of the invention as hereinafter set forth and claimed.

In the drawings:

Figure 1 is a vertical elevation partly in section of a cathode structure including the improved heater unit.

Figure 2 is a vertical elevation of a heater unit before it is assembled in a cathode tube.

Figure 3 is a vertical elevation of a modified form of heater unit.

Figure 4 is a vertical elevation of a further modified form of heater unit Figure 5 is a perspective view of one of the insulating collars.

\ Figure 6 is an elevation showing a filament wire with collars threaded thereon preparatory to the winding operation.

Figure 7 is an elevation partly in section, showing the machine for carrying out the winding operation.

Figure 8' is a view similar to Figure 6 but showing the relation of parts after the wire has been twisted.

Fig. 9 is a vertical elevation partly in section of a modification of the cathode structure.

Referring to the drawings more particularly, the tube 10 is the conventional cathode tube covered with an emissive coating 11 and provided with a tab 12 for connection.

. mm m ma GATEODES OI VACUUM TUBES AND METHOD OF PRODUCING SAME Serial No. 514,156.

to a suitable conductor, as well understood in the art. The heating element 13 is connected to suitable conductors 14, and is suported and insulated both from itself and rom the cathode 2 by collars 15 and 16,' and by the central road 17. The parts 15, 16 and 17 may be made of any suitable insulating material, such as magnesium oxide. The collars 15 and 16 are formed with the central opening 18, as shown in Figure 5, and with two side apertures 19 for-passage of the filament wire. i

In the process of forming the heater unit the filament wire is first bent back upon itself to the hairpin form illustrated in Figure 6, and the two free ends are then threaded through the side apertures 19 of the upper collar 15 and the lower collar 16 to the position indicated in Figure 6. This assembly is then placed over the needle of the winding machine as shownin Figure 7.

Thewinding machine includes a suitable support 20 carrying a guide member 21 A sleeve 22 projects downwardly from the memher 21 and is internally threaded for co-open ation with a threaded sleeve 23, which is connected as by a set screw 24 to the shaft 25. The upper end of shaft 25 carries the needle 26 which projects upwardly through an opening in the guide 27. Suitable means not shown is provided for rotating shaft 25. After the preliminary filament assembly has been placed over the needle to the position of Figure 7, the operator grasps the lower collar 16 and holds it agamst movement. Shaft 25 is then rotated and this rotation together with the 00-0 erative threads on 22 and 23 causes the nee Is to rotate and advance upwardly simultaneously. This op eration is continued until substantially all of the filament has been twisted, leaving the lower ends straight for attachment to the conductor 14. The filament assembly is now removed from thewinding machine and is in the form shown in Figure 8, with the filament wire forming a double helix between the collars 15 and 16. a

The insulating rod 17 is now inserted through the bores 18 to roduce' the heater assembly of Figure 2 and this heater assembly When the filament assembly is in the condition illustrated inFigure 8, a slight rotation of collar 16 relative to collar 15 will cause the op osite leads of the filament wire to contact with each other just above the collar 16. If this filament assembly is inserted within the cathode tube without any rotating of the collar 16 relative to the collar 15, and these collars can be held against subsequent relative rotation, it isunnecessary to use a central insulating rod 17 as the collars 15 and 16 provide suflicient insulation and support for the filament. And while such a structure requires more accuracy in assembly than is at present practical in commercial production,

, the present invention is broad enough to include it. a

In the preferred form a complete central sup ort rod extending through both collars is use as at 17 in Figure 2. This rod keeps the coils'from contacting in the manner just explained and holds the filament coil rigidly centered in the cathode tube. However a or with a rod 17 extending the full length 0 short section of insulating rod may be inserted through the lower collar 16 and into the lowermost several coils of the filament, as at 17 in Figure 3, and such a section is sufiicient to prevent the short-circuiting of the coils just above collar 16 due to relative rotation of collars 15 and 16.

.It is ossible by the method disclosed herein to p ace more than two collars on the filament, and while any desired number of the collars may be used, the preferred number is either two as in Figure 2, or three as illustrated in Figure 4, the third collar being placed at the center of the filament as an additional precaution against the center of the filament being knocked into contact with the cathode by excessive vibration or a heavy blow gem outside. I Th2 multiplila) e c3181; assem y o igure can 0 course without a central rod, aslillustrated in that figure, or with a short rod 17' as in'Figure 8 A further modification is shown-in'Figure 9. Im producing thefilament assembly used the filament as in Figu in this form onlythe lowercollar '16 is as-.

sembled on the wire before twist? ,andafter twisting the assembly is like th showp in vacuum tubes or during its subsequent use.

Figure 8 but without the upper collar 15. This filament assembly is then inserted into the cathode tube 10, and a collar 28, which has a center bore large enou h' to accommodate the twisted filament, is'p aced in the upr end of the cathode tube and serves to insulate the upper end of the filament. Collar 28 may have a press fit in the cathode tube, or

it ma be retained in place by an other preferre means. A support rod 1 preferably extends through the lament for its entire len%th although a short rod 17' may be used in t e lower end only if desired.

It will be understood by one skilled in the art that the present invention provides an efiicient and easily assembled means for insulating filaments of the coiled tygie without using insulating coatings on the ament.

I claim: A

. 1. A device of the character described comprising a filament wire formed into a double elix, an insulatin collar at each end of the helix, each col ar being formed with a central aperture, a rod passing through the central aperture of each collar and through the central axis of the helix, each collar being formed with two side apertures spaced from the central aperture, the filament wire passin through both 'side apertures of each co lar. A 3

2. A device of the character described comprising an upper insulating collar formed with at least two apertures, a filament wire passing through one of the first-named apertures and being bent back uponiitself beyond the collar and passing through the other of the first-named a rtures, a lower insulatin collar forme with a central a rture an two side apertures, each lead of e wire passing through one of said'side apertures, the two leads of the wire between the collars .beingtwisted into a double helix, and an insu ating rod extending through said central a rture and through several turns of the he ix adjacent to the lower collar.

3. A cathode assembly for vacuum tubes comprising a cathode tube, a pair of insulating collars, one of the collars being located within each end of the tube, each collar being formed with a central aperture and two s1 e apertures spaced from the central a rture, a filament wire passing through th apertures of each collar, the portions of the wire lying between the collars being twisted into a .double helix, and an insulatin rod passing through the central aperture 0 each iollliar and through the central axis of the e x. a

'4. A cathode assembl for vacuum tubes comprising a cathode tu an upper insulating collar-located within the upper end of the tube and formed with two side apertures,'a lower insulating collar located within I the lower end of the tube and formed with o'oentral apertune and two side apertures, a

filament wire passing through both side aper-- tures of each collar, the portions of the wire lying between the collars being twisted into a double helix, and an insulating rod passing through the central aperture of. the lower 'co ar and through several turns of the helix adjacent to the lower collar.

5. The method which comprises providin a plurality of insulating collars, each 0 which is formed with at least two apertures, bending a piece of filament wire into hairpin shape'and threading the free ends of the wire through respective apertures in each collar, to a position in which the collars are located close to each other at the bend of the wire, twisting one collar with respect to the other, and increasing the distance between the collars thereby twisting the wire into a double helix between the collars.

6. The method which comprises providing a pair of insulating collars, each of which is formed with a central aperture and with two side apertures, bending a piece of filament Wire into hairpin shape and threading the free ends of the wire through respective side apertures in each collar to a position in which the collars are located close to each other and near the bend of the wire, inserting a forked needle through the central apertures of the collars and into engagement with the bend ofthe wire, holding stationary the collar farthest from the bend of the wire, rotating the needle and moving its forked end away from the stationary collar, thereby twisting the wire into a double helix between the collars, removing the needle, and inserting an insulating rod through the central;

aperture of each collar and through the central axis of the helix.

7. A cathode assembly for vacuum tubes comprising a cathode tube,-a lower insulating collar located within the lower end of the tube and formed with a central aperture and two side apertures, an uncoated filament wire passing through both side apertures, the portionv of the wire above the lower collar being twisted into a return helix, and a collar insulating the upper end of the helix from the cathode tube.

8. A cathode assembly for vacuum tubes comprising a cathode tube, a lower insulating collar located within the lower end of V the tube and formed with a central aperture and two side apertures, an uncoated filament wire passing through both side apertures, the

portion of the wire above the lower collar eing twisted into a return helix, and an upper insulating collar located within the upper end of the cathode tube and formed with a central aperture large enough to accommodate the helix, the helix extending into the aperture of the upper collar. 7

' WALTER J. SKINNER. 

